In a wireless communications system, a higher transmit power, with which user equipment (UE) sends an uplink signal to a base station, indicates a longer transmission distance of the uplink signal, and correspondingly, the uplink signal has greater interference in the base station.
A nominal transmit power P1 of UE is determined by a power level corresponding to a hardware capability of the UE, and P1 is a maximum power that can be used by the UE to send an uplink signal. To extend a transmission distance of the uplink signal as much as possible and reduce interference from the uplink signal to the base station as much as possible, usually a maximum transmit power Px of the UE needs to be further limited below P1.
The base station sets a limiting power P2 in advance according to the power level of the UE, and sends the limiting power P2 to the UE. The UE determines Px according to the limiting power P2, where an upper limit of Px does not exceed a smaller value between P1 and P2. For example, in a communications system, a power level of UE is class 3, and a corresponding nominal transmit power P1 is 23 dBm. The base station may set a limiting power P2 to 20 dBm, and delivers the limiting power P2 to the UE within a communication range of the base station. The UE determines an upper limit and a lower limit of a maximum transmit power Px according to the limiting power P2, where the upper limit of Px does not exceed 20 dBm.
In the prior art, an expected effect, that is, extending the transmission distance of the uplink signal as much as possible and reducing interference from the uplink signal to the base station as much as possible, can be achieved only when the base station sets limiting powers for multiple UEs having a same power level.